Electron shock drift acceleration at a low-Mach-number, low-plasma-beta quasi-perpendicular shock

TL;DR

This study uses particle-in-cell simulations to demonstrate that electron cyclotron drift instability significantly enhances electron acceleration efficiency at low-Mach-number, low-beta quasi-perpendicular shocks.

Contribution

The paper reveals the role of electron cyclotron drift instability in boosting shock drift acceleration efficiency in low-beta plasma shocks.

Findings

Electron cyclotron drift instability excites electrostatic waves at the shock front.

Electrostatic waves scatter and heat incident electrons, aiding their escape from the loss cone.

Enhanced shock drift acceleration results from this process.

Abstract

Shock drift acceleration plays an important role in generating high-energy electrons at quasi-perpendicular shocks, but its efficiency in low beta plasmas is questionable. In this article, we perform a two-dimensional particle-in-cell simulation of a low-Mach-number low-plasma-beta quasi-perpendicular shock, and find that the electron cyclotron drift instability is unstable at the leading edge of the shock foot, which is excited by the relative drift between the shock-reflected ions and the incident electrons. The electrostatic waves triggered by the electron cyclotron drift instability can scatter and heat the incident electrons, which facilitates them to escape from the shock's loss cone. These electrons are then reflected by the shock and energized by shock drift acceleration. In this way, the acceleration efficiency of shock drift acceleration at low-plasma-beta quasi-perpendicular shocks is highly enhanced.